The small bright dot visible in the centre of the picture is a single positively-charged strontium atom, held almost motionless by electric fields emanating from the metal electrodes surrounding it. (The distance between the small needle tips is about two millimetres.)
When illuminated by a laser of the right blue-violet colour, the atom absorbs and re-emits light particles sufficiently quickly for an ordinary camera to capture it in a long exposure photograph.
This picture was taken through a window of the ultra-high vacuum chamber that houses the trap. Laser-cooled atomic ions provide a pristine platform for exploring and harnessing the unique properties of quantum physics. They are used to construct extremely accurate clocks or, as in this research, as building blocks for future quantum computers.
The photo won first place in the 2018 science photography competition held by the UK’s Engineering and Physical Sciences Research Council.
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